Paper drying machinery



June 11, 1968 F. H. SUTTON 3,387,384

PAPER DRY ING MACH INERY Filed March 30, 1966 INVENTOR.

FREDERIC H. SUTTON ATTORNEYS United States Patent 3,387,384 PAPER DRYING MACHINERY Frederic H. Sutton, Metairie, La., assignor to The Black Clawson Company, Hamilton, Ohio, a corporation of Ohio Filed Mar. 30, 1966, Ser. No. 538,823 6 Claims. (Cl. 34-114) ABSTRACT OF THE DIStCLOSURE heated air from the central portion of each pocket towards both open ends for purging humid air from the pocket.

This invention relates to drying machinery for a newly formed paper web or the like, and more particularly to improved apparatus of economical construction for minimizing accumulation of humid air Within the machinery so that the paper web can be efficiently dried.

The present invention has special relation to drying machinery including a series of parallel spaced heated drying drums and employing felts for holding the paper web in firm contact with the outer surface of each drum. As a result of the closely spaced arrangement of the drying drum and guide rollers for directing the felt to obtain maximum contact between the paper web and each drying drum, and elongated pocket is produced or defined between each drum and the adjacent portions of the felt and paper webs.

It has been found that in operation of the machinery, each of these elongated open-ended pockets, which extend the width of the paper web, tends to accumulate humid air which results from evaporation of moisture from the corresponding drum and adjacent portions of the felt and paper webs. If this humid air is not removed from each pocket, the overall drying operation becomes less efficient since the paper web retains a larger percentage of moisture due to the reduced capacity of humid air to pick up additional water in a uniform manner.

In view of the trend towards wider and higher speed paper making machinery to increase the capacity for producing paper, the problem of accumulating humid air within the longer pockets has become increasingly more significant. Furthermore, it is generally necessary to employ a substantial number of dryer drums to provide for high speed drying of the web, and thus the cost of constructing a purging device for each pocket is significant.

Accordingly, it is a primary object of the present invention to provide improved and simplified apparatus for use on paper drying machinery for effectively and efliciently purging humid air from each elongated open ended pocket defined by a dryer drum and adjacent portions of the felt and paper webs.

Other objects of the improved apparatus of the invention are to provide a purging of humid air from an elongated pocket which is effective to produce a condition of substantially uniformly low humidity throughout the Patented June 11, 1968 entire length of the pocket; to provide a combined purging system and doctor member which cleans the surface of the dryer drum for minimizing the cost of constructing a purging system for each pocket; to provide a combined purging system and doctor member along with means for maintaining the doctor member at a uniform temperature to prevent distortion of the doctor member; to provide a purging system wherein opposing streams of heated air are directed outwardly from the center of each pocket towards both open ends for obtaining an eificient use of the heated air and effective displacement of humid air; to provide a combined purging system and doctor member which has substantial rigidity in addition to being simple and economical in construction; and to provide a combined purging system and doctor member which can be oscillated to obtain effective cleaning of the dryer drum surface.

Still other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawing:

FIG. 1 is a diagrammatic side view of drying apparatus showing the preferred locations of each combined purg' ing system and doctor member constructed in accordance with the invention;

FIG. 2 is a fragmentary view of the drying apparatus as generally taken along the line 2-2 of FIG. 1;

FIG. 3 is an end view of the combined purging system and doctor member as taken generally along the line 3-3 of FIG. 2;

FIG. 4 is a somewhat enlarged fragmentary view of one end portion of a combined purging system and doctor member of the invention and with a portion broken away to show details of construction;

FIG. 5 is a sectional view of the combined purging system and doctor member taken along the line 5--5 of FIG. 2; and

FIG. 6 is a sectional view similar to FIG. 4 taken along the line 6-6 of FIG. 2.

In the drawing, which illustrates a preferred embodiment of the invention, the dryer section shown schematically in FIG. 1 generally includes a series of closely arranged and parallel spaced, steam heated dryer drums 10 which are mounted on corresponding shafts 12 rotatably supported by suitable bearings between parallel spaced side walls 13 (FIG. 2) forming a part of a main frame (not shown). A newly formed paper web W is directed from the guide roll 14 around the outer surface of each drum It? in a manner to provide a maximum area of contact between the web W and the heated surface of the drum.

Also supported by the frame walls 13 are a series of guide rolls 15 around which an endless or seamed felt F is directed for holding the paper web W in firm contact with the heated surface of the drums 10. It is to be understood, however, that the term felt as used herein not only includes conventional dryer felts constructed from cotton, wool or asbestos but also includes other means for holding the paper web in firm contact with the dryer surface such as the newer plastic dryer screens and impervious belts.

An elongated pocket 18 is defined by each of the drums 1t} and the corresponding guide roll 15 and adjacent portions of the paper web W and the felt F. Each pocket 18 extends the full width of the paper web W, and as a result, the moisture which initially evaporates from the surface of the drum 10 and adjacent portions of the paper web W and felt F tends to accumulate within the air in the pocket. This accumulating moisture reduces the evaporation of moisture from the web W.

In accordance with the present invention, there is positioned within each pocket 18 (FIG. 1) a doctor assembly 2%! comprising a doctor blade 22 and a supporting beam of hollow section. Thus as shown in FIGS. 2 and 3, the doctor assembly includes an elongated angle section or beam 24 and an elongated plate section 25 which is connected to the beam 24 to define an elongated passageway 28 extending the length of the drums fit and having a generally triangular cross-sectional configuration.

A doctor blade 22 is mount-ed on each angle beam 24 by an elongated member 3%), and the blade 22 is positioned to engage the outer cylindrical surface of the associated drum 10 to maintain the surface free of dirt and other particles. End walls 32 (FIG. 4) are connected to each end of the sections 24 and 26, and aligned shafts 33 and 34 extend outwardly from the corresponding end Walls 32. The shafts 33 and 34 are rotatably supported within corresponding bearings 35 mounted on a frame member 3.; connected to the walls 13 and thereby support the doctor assembly 26 within the corresponding pocket 18. Also, the shafts 33 and 34 are adapted to slide axially within the corresponding bearings 35 to enable the doctor assembly 20 to move longitudinally.

A cam follower 37 (MG. 4) is mounted on the outer end portion of the shaft 33 outboard of the bearing 35 and includes a pair of parallel spaced fiat surfaces 33. A motor driven gear reduction unit 40 is mounted on the frame member 36 and has an upwardly extending output shaft 42 on which is mounted a cam 44 having an eccentrically positioned cylindrical surface 45 which is spaced between the flat surfaces 38. The purpose of the unit 4-9, cam 44 and the follower 35 is to oscillate or reciprocate the doctor blade 22 so that it oscillates longitudinally while in contact with the outer surface of the corresponding drum 10 and thereby provides an effective cleaning of its surface. It is to be understood, however, that the specific construction of the oscillating mechanism for the doctor blade 22 forms no part of the present invention as other means of inducing an oscillating motion to the doctor may be employed with equal effectiveness.

An arm is rigidly mounted on the shaft 33 between the bearing 35 and the doctor assembly 2t and is engaged by a cam 52 mounted on a shaft 53 rotatably supported within a bearing 55 mounted on the frame member 36. A handle or lever 56 is secured to the outer end portion of the shaft 54 for rotating the cam 52, which in turn rotates the shaft 33 and doctor assembly'Ztl to pivot the doctor blade 22 away from the outer surface of the drum 10 when it is desired to clean the blade 22.

Referring to FIGS. 2 and 5, an inlet duct 60 defining a chamber 61, is mounted on the end portion of each doctor member adjacent the shaft 34 and is connected by a flexible conduit 62 to a suitable source of heated dry air for supplying the air through an opening 63 (FlG. 5) and into the passageway 23 defined within the doctor assembly 20. As shown in FIG. 6, an outlet opening 65 is formed within the back side of the angle 24 at the midpoint of the doctor member which is also the center of the corresponding pocket 18. While this central outlet opening provides a simplified form of the invention, it is to be understood that multiple openings strategically spaced along the back side of the doctor may also be used without departing from the scope of the invention.

Covering the outlet opening 65 and rigidly secured to the back side of the angle section 24 of each doctor assembly 20 is a semi-cylindrical deflector 68 which defines a semi-cylindrical passageway 76 open at both ends. Also a small outlet opening 72 (FIG. 6) is formed within the deflector 68 at its midpoint.

Referring to FIG. 4, a small bleed opening 75 is formed within the end wall 32 of the doctor assembly 20 at the opposite end of the passageway 28 from the inlet opening 63. This opening '75 is provided to permit a small continuous supply of heated air through the entire length of the doctor assembly 20 and past the outlet opening 65 for maintaining the doctor assembly at uniform temperature and thereby preventing its distortion due to a temperature differential.

In accordance with one successful installation of doctor assemblies 20 constructed in accordance with the invention, the passageway 28 was constructed to have a crosssectional area of approximately 25 square inches, and heated air was supplied through the conduit 62 and inlet duct 60 at a variable rate relating to the grade and basis weight of the paper. In addition, the total outlet area of both ends of the passageway 70 was approximately 46 square inches which provide for a controlled discharge velocity of heated air from each end of the passageway 70.

As a result of the construction of the deflector 68, the heated air is discharged from the passageway 76 in opposing directionally controlled streams towards the open ends of the elongated pocket 18. In addition, a stream of heated air is directed out of the centrally located outlet opening '72 formed in the deflector 68 to provide for complete purging of moisture laden air from the pocket 18.

It can be seen that a combined doctor member and purging system constructed in accordance with the present invention provides several desirable features and advantages. Basically, it has been found that by directing opposing streams of heated air from substantially the center of from points along the doctor back of each of the pockets 18 towards the corresponding open ends, humid air is prevented from accumulating within the pocket by an effective purging operation which produce a substantially uniform condition of humidity throughout the entire length of the pocket 18 and thus across the full width of the paper web W. That is, by introducing the heated dry air into the central portion of the pocket where the humidity is normally higher, the opposing streams of air effectively displace the humid air and force it out of the open ends of the pocket. Also this manner of purging does not produce a loss of heated dry air directly into the atmosphere and thus provides for a highly emcient use of the available heated air.

Another important feature is provided by the construction of the doctor assembly 20 so that it also serves as a conduit for supplying heated air to the center of the corresponding pocket 18. That is, the angle section 24 provides substantial strength and rigidity and by simply adding the plate section 26, the angle section is converted to form the passageway 28. It has been found that this construction not only provides a rigid support for the doctor blade 22 but also provides an economical means for supplying hot dry air to the center of each pocket 18. Still another feature is provided by the bleed opening formed within the end wall 32 of the doctor assembly 20 for allowing a small quantity of heated air to escape and thereby maintain the doctor member at a uniform temperature along its entire length so that it is not distored due to difference in temperature along its length.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In machinery for drying a newly formed paper web or the like and including a plurality of parallel spaced dryer drums around which an endless felt is directed for holding the paper web in firm contact with such drums, improved apparatus for cleaning the surface of each drum and preventing the accumulation of humid air within the open ended elongated pocket defined by each such drum and the adjacent portions of the felt, comprising an elongated doctor assembly extending within said pocket across the width of the felt and defining a longitudinally extending passageway, means supporting said doctor assembly in parallel spaced relationship with such drum, said doctor assembly including a longitudinally extending doctor blade movable into engagement with the outer surface of such drum, means for introducing a supply of heated air into one end portion of said passageway, means defining at least one outlet opening from said passageway and disposed generally within the central portion of the pocket, and means associated with said outlet opening for directing streams of heated air outwardly and laterally from said pocket towards both open ends thereof for effectively purging humid air from the pocket and producing a condition of substantially uniformly low humidity across the width of the web.

2. Apparatus as defined in claim 1 wherein said doctor assembly includes a hollow beam member defining said passageway and providing the sole support for said doctor blade, and means for rotating said beam member to move said doctor blade into engagement with the outer surface of said drum.

3. Apparatus as defined in claim 2 wherein said hollow beam member includes an elongated section having an L- shaped cross-sectional configuration, and an elongated plate section connected to said L-shaped section to define said passageway while providing said beam member with substantial rigidity.

4. Apparatus as defined in claim 1 including means for oscillating said doctor assembly in a longitudinal direction, and flexible conduit means connected to said beam member for introducing said heated air into said end portion of said passageway while said doctor blade is oscillating with said beam member.

5. Apparatus as defined in claim 1 wherein said means for directing said streams of air laterally from said outlet opening towards the open ends of said pocket includes a deflector mounted on said passageway means in covering relationship with said outlet opening and defining a passageway having open end means through which the heated air is discharged for purging humid air from said pocket.

6. Apparatus as defined in claim 1 wherein said doctor assembly includes means defining a bleed opening from an end portion of said passageway opposite the end portion where heated air is introduced to provide for a continuous low volume flow of heated air through said doctor assembly to maintain said assembly at a substantially uniform temperature along its length for preventing distortion thereof.

References Cited UNITED STATES PATENTS 1,214,712 2/1917 Pope 34--114 1,267,70l 5/1918 Schenck 34-117 2,285,290 6/1942 Lang 34-114 FOREIGN PATENTS 158,843 2/1933 Switzerland.

FREDERICK L. MATTESON, JR., Primary Examiner.

H. B. RAMEY, Assistant Examiner. 

